Verifying Performance
FID checkout
Released: March 2004 6850 Series II GC User Information page 64 of 256
Background offset checks
1. If lit, turn the FID flame off.
2. Display the signal output to determine flame-off background offset. A
stable value of < 2.0 display units is acceptable. If > 20 display units, clean
the detector as described in “Maintaining a flame ionization detector
(FID)” on page 187.
3. Ignite the FID flame. You should see an increase in detector output to a
stable value.
If not, hold a cool, shiny metal object, such as a chrome-plated wrench,
just above the FID chimney. You will see water condensation if the flame
is lit.
If the flame has not ignited, recheck all flow rates and gas source pres-
sures. If the flame still cannot be lit, see “The flame goes out or will not
light” on page 188 for more information.
4. With the flame lit, observe the FID signal at the display. This is the
flame-on background offset. A stable value between 5 and 20 display units
is acceptable. If an air cleaning system is being used, the signal may
stabilize below 5.
If the value is > 20 display units, system bakeout is necessary. See
“Thermal cleaning (bakeout)” on page 185 for details.
If the value is < 5 display units, verify that the electrometer is on. If it was
off, recheck the flame-off background offset. If it was already on, your
detector requires service.
Oven
Initial temp 40°C
Initial time 0 min
Rate 1 25°C/min
Final temp 90°C
Final time 0 min
Rate 2 15°C/min
Final temp 170°C
Final time 2 min
Table 18. FID Checkout Conditions (Method FIDCKO) (Continued)
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